java.sql.SQLException：结果集开始之前/之后

我遇到了让我的程序从数据库中读取信息的问题。我希望它基本上打印出提取信息的表格（我遵循的教程就是这样做的）。不幸的是，在翻阅我的代码和教程后，我发现没有什么区别。最终我希望能够从数据库中获取信息，并允许用户编辑这些信息。java.sql.SQLException：结果集开始之前/之后

这里是我的代码：

import java.sql.*; 

public class Main { 
//Driver and connection URL. 
private String JDBC_DRIVER = "com.mysql.jdbc.Driver"; 
private static String connectionString = "jdbc:mysql://localhost/employees"; 

//DB Credentials. 
private static String password = "password"; 
private static String username = "root"; 

public static void main(String[] args) { 
    // TODO Auto-generated method stub 

    Connection connection = null; 
    Statement statement = null; 
    ResultSet resultSet = null; 

     try { 
      //Register JDBC Driver. 
      Class.forName("com.mysql.jdbc.Driver"); 
      connection = DriverManager.getConnection(connectionString,  username, password); 
      System.out.println("Connected to database."); 


      statement = connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE); 


      resultSet = statement.executeQuery("SELECT * from employees"); 

      //process query results. 
      ResultSetMetaData metaData = resultSet.getMetaData(); 
      int numberOfColumns = metaData.getColumnCount(); 
      System.out.println("Emloyees table of Employees DB"); 

      for (int i=1; i<=numberOfColumns; i++){ 
       System.out.printf("%-10s\t", resultSet.getObject(i)); //Return the value of a given object as a java object. 
      } 
      System.out.println(); 

      //Initial cursor is before first row. 
      while(resultSet.next()){ //move cursor forward one row. 
       for (int i=1; i<=numberOfColumns; i++){ 
        System.out.printf("%-10s\t", metaData.getColumnName(i)); 
       } 
      } 
      System.out.println(); 


     } catch (Exception e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } finally { 
      try{ 
       connection.close(); 
       statement.close(); 
       resultSet.close(); 
      } 
       catch(SQLException se){ 
        se.printStackTrace(); 
       } 
      } 
     System.out.println("Great! Everything works!"); 
     } 

}

这里是我的什么，当我运行的程序发生了：

Fri Aug 12 19:49:55 EDT 2016 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification. 

Connected to database. 
Emloyees table of Employees DB 
java.sql.SQLException: Before start of result set 
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:963) 
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:896) 
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:885) 
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860) 
at com.mysql.jdbc.ResultSetImpl.checkRowPos(ResultSetImpl.java:790) 
at com.mysql.jdbc.UpdatableResultSet.checkRowPos(UpdatableResultSet.java:214) 
at com.mysql.jdbc.ResultSetImpl.getObject(ResultSetImpl.java:4432) 
at Main.main(Main.java:38) 
Great! Everything works!

值得注意的是：它是连接到数据库，如果我换我的for循环使用我的while循环，它会多次打印每列的名称，java.sql.SQLException将在结果集的开始之后而不是之前发生。

来源

2016-08-13 user338098

你的代码没有意义。除非next()返回true，并且您不需要在循环中调用ResultSet.next()来打印列名称，否则不能调用ResultSet.getObject()。它们不会每行更改。

也可以假定您想要在数据之前打印列名称。

打印列名称的循环应该是打印getObject()值的循环的地方，反之亦然。

来源

2016-08-13 00:06:41 EJP

java.sql.SQLException：结果集开始之前/之后

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